to the point where she was assuming some of those roles of a girlfriend
I've gone through something like this, and honestly I have to say it's better not to let it happen. You become dependant on a person who, however, isn't bound to you in any way since you're not romantically engaged, and this causes you to, how to say it..slow down in your life because you want to go at the same pace of someone whom however doesn't include you on their path. Also potential heartache if it's love love.
Sometimes even a person you love dearly can be truely what holds you back the most. In relationships with others, in your own projects for the future.
I'm not saying break up, but I think it's really important to not be dependant on that person, look around, find new people, don't think of her as 'the one'.